Recently, as energy consumption is increased, solar cells to convert the solar light into electrical energy have been developed.
A solar cell (or photovoltaic cell) is a core element in solar power generation to directly convert solar light into electricity.
For example, if the solar light having energy greater than bandgap energy of a semi-conductor is incident into a solar cell having the PN junction structure, electron-hole pairs are generated. As electrons and holes are collected into an N layer and a P layer, respectively, due to the electric field formed in a PN junction part, photovoltage is generated between the N and P layers. In this case, if a load is connected to electrodes provided at both ends of the solar cell, current flows through the solar cell.
In particular, a CIGS-based solar cell, which is a PN hetero junction apparatus having a substrate structure including a glass substrate, a metallic back electrode layer, a P-type CIGS-based light absorbing layer, a high-resistance buffer layer, and an N-type window layer, has been extensively used.
However, according to the related art, when a CdS layer, which serves as a buffer layer, is grown, the cost of disposing waste materials is increased due to the high toxic CdS, so that the cost of fabricating the solar cell is increased.